Climate Change Is Making Pathogens Worse

In this exclusive video, Camilo Mora, PhD, professor in the Department of Geography and Environment at the University of Hawaii at Mānoa, discusses his team’s recent study on the impact of climate change on human pathogenic diseases.

The following is a transcript of his remarks:

At the beginning of the COVID pandemic, obviously there was a huge interest in whether this disease was being caused or was caused by climate change. So we decided to investigate this, and very early on we realized that we were not going to get enough access to the data that was required to answer that question.

But while we were doing that search, we found many case examples. In fact, over 20 different case examples that allow [us] to justify climate change, regardless of whether climate change caused COVID or not, we had at least 20 different ways that we can explain COVID.

Let me just give you an example. You think about the craziness of COVID, all of the people around the world that died, the people that got sick, the economic loss of COVID. You think about all of that nightmare, and all of that nightmare goes back to a single incident between a person and a wild animal infected with that virus. That event is called a spillover. So that event, it turns out that it might look very insignificant, but it was the thing that pulled the trigger that made COVID such a big problem at that moment.

Climate change has many different ways that could have caused that spillover. Imagine that bat in the middle of the jungle somewhere — this animal is right there with all the pathogens and we are over here living nicely. We have no conflict with them. We go [to the jungle] with climate change.

Basically, we’re talking about droughts now that force those animals to travel farther away in their search for food. You can also think about wildfires, which now are being aggravated by the drought and the heat, and now this bat loses its habitat; what do you think that animal is going to do? It’s going to start traveling farther away, coming into contact [with people], and then increasing the chances that we generate that first spillover.

We generated a question, and the question is: how many diseases can be affected by climate change?

So what we did is we took every single disease that is registered, almost since the end of the Roman empire, until now. Lucky for us, somebody had collected that data already, so there is a very nice list of diseases. What we did was to take every single one of the diseases and see in the scientific literature if it has been affected by any one of 10 different climatic changes.

When we did that systematically, looking just for case examples in places around the world, we found over 3,000 case examples. Those 3,000 case examples can be clustered in the four different ways in which climate change has impacted humanity.

So the first one was — here is the pathogen, and this is you. The first way is climate change forcing many of these pathogens to move. As a result, they come into contact with us. And in that case, you had hundreds of examples – we just explained the case example with the bat.

The other mechanism that we’ve encountered was climate change forcing us to move. You can think about a wildfire where everybody has to run away, you can think about a flood, a hurricane — everybody has to move. And in that movement we are now the ones that encroach into the habitat of the pathogens, then creating that spillover.

The third mechanism was actually climate change making many of these pathogens worse. So just to give you an example, think about heat waves. When heat waves reach temperatures of 40 or 42 degrees [Celsius; about 104°F to 108°F], basically what is happening out there in the wild is a process of natural selection in which you are selecting bacteria and viruses that can tolerate that kind of heat. When a pathogen like that goes and infects a human being, we don’t have a mechanism to deal with that because fever just cannot do anything to the virus or to the bacteria because they’re already adapted to survive temperatures that hot.

The last mechanism was climate change making us weaker, and we encounter many examples of this. This actually happens many different ways. You can think about a hurricane or a flood disrupting the access of people to healthcare such that they get sick. They just don’t have a doctor or medicine or anything for them to get prevented [from illness], so that actually reduces the extent to which we can cope with these pathogens once we get infected.

Once we compiled the entire list of diseases that we know had impacted humanity and looked for scientific papers that had shown that climatic change affecting that disease, we found that, of all of the diseases that had ever impacted humanity that there is a record of, 58% of those diseases had been affected at some point by those climatic changes. What that reveals to me is the magnitude of the vulnerability that we are under.

The analogy that I like to use is: imagine that I get in a fight with Mike Tyson. I think that I’m strong enough to get in a fight with Mike Tyson and maybe punch him once or twice, and he’s going to kick my butt. Now put in the same analogy Arnold Schwarzenegger, Sylvester Stallone, and Jackie Chan, and now you have all of those guys fighting against me. There is no way I’m going to be surviving those four guys. I can barely survive one! What is the chance I’m going to survive four?

As it comes down to climate change, what we are talking about here is over 200 diseases that can be made worse by climate change, all of them coming and attacking us in over 1,000 different ways. So for me, one of the obvious conclusions of this paper is that there is no way we are going to be able to adapt to climate change.

Add to this recipe the adaptation that we will need to cope with the heat, the adaptation for the floods, the adaptation for the wildfires, the adaptation for the hurricanes, and you’ll realize how overwhelming climate change is going to become and the amount of suffering that it’s going to create for us if we don’t deal with this problem seriously and, I think, right now.